An amount of data (e.g., content data) stored in a storage system has been steadily increasing. When a large number of storage devices are mounted in order to increase a data amount storable in the storage system, costs of the storage system increase. This is unfavorable for a user. Therefore, there is a technique for substantially increasing the storable data amount by compressing and storing data.
In recent years, a storage device (e.g., a SSD (Solid State Drive)) in which a flash memory is used as a storage medium is used for a storage system. The SSD can perform high-speed input and output compared with a HDD (Hard Disk Drive). However, since bit cost of the SSD is high compared with the HDD, there is a demand for a technique for reducing the bit cost by compressing and storing data. The compression of the data is performed by a controller or the storage device of the storage system. The controller of the storage system controls the entire system such as input/output processing and copy processing for the data. When the controller of the storage system is caused to execute compression processing, this causes performance deterioration of the entire system. Therefore, there is a technique in which the storage device executes the data compression (PTL 1).